Micro-power (short-range) wireless communication technology has emerged since the end of the last century, and it has been widely used in the following fields including industrial control, home intelligence, wireless remote control, security alarm, environmental monitoring, smart meter reading, toxic and harmful gas monitoring, logistics, RFID and the like after ten years of development. In recent years, the Internet of Things has been regarded as a new growth point of the future economic development after the financial crisis in domestic and international ranges. As a result, the short-range wireless communication technology will further develop in the applications of Internet of Things (especially sensor network).
The concept of Internet of Things is almost appearing at the same time with the low-carbon economy. As one of the primary communication means for the Internet of Things, the short-range wireless digital communication technology is bound to develop towards the direction with low power and micro power while complying with the developing trend that demands low-carbon and low energy consumption. In addition, battery-powered products become more and more and much stricter with the power consumption with the increasing spread of applications of mobile communication devices.
So, how to reduce the overall power consumption of the wireless communication device? Obviously, it is unrealistic only to decrease the transmitting power of the transmitter or only to reduce the current consumption of the receiver. The effect of this method is not obvious, and it will also result in harsh consequences, namely reduction in communication quality. The purpose of reducing power can be achieved only by forcing the communication device to sleep at idle period which can greatly reduce the average power consumption of the communication device. At the same time, the life of battery can be prolonged several times or even thousands of times in the battery-powered devices.
For half-duplex wireless communication system or network composed of two or more wireless transceiver devices with any structure or protocol, the time that a certain device works in transmission or reception is indeed very little. It can greatly reduce the average power consumption by making the communication device enter the sleep mode when it does not work in transmission or reception. Since the current consumption in the sleep mode is only at a microampere level and even can be a few microamps, while the transmitting current of the wireless communication device is more than tens of milliamps and the receiving current is between a dozen milliamps and tens of milliamps, the longer the sleeping period is, the lower the average power consumption of the communication system that employs the sleep mechanism is.
When a single or a group of wireless communication devices are in the sleep mode without receiving or transmitting, i.e. in a non-working state, communication will fail when other communication devices demand to communicate with them. Thus, a set of processes or methods are preferred to make the wireless communication device in the sleep mode perceive and perform communications when other devices need to communicate with it, that is, to awaken the wireless communication device in the sleep mode. Currently, there have been many methods to awaken the wireless communication devices from the sleep mode such as waking up regularly, waking up through certain signal strength and waking up through data packet. However, regarding these waking-up methods, some require synchronization in time for all communication devices in the wireless communication system, some are weak in the anti-interference capability to cause a false awakening, and others take a long time during the detection period which leads to large power consumption. Besides, communication protocol and communication process are relatively complex and last for a long time as well.